Collision-induced decoherence and thermalization

We study the state change in an N-level system induced by collisions with moving massive particles with d-internal levels. The relation between the width of the wave packet of the incident massive particle and the energy level spacing determine if populations and coherences evolve coupled or uncoupled. In the latter case, the target system decoheres as identical consecutive collisions occur [1]. If narrow (in momentum space) wave packets have average momentum distributed with the effusion distribution, the target system thermalizes. The energy exchange can be interpreted as heat. In the limit of very broad wave packets, the collision induces a change of energy but keeps the entropy unchanged. The collision performs work on the target system [2]. These results show that thermodynamic processes can be implemented in collision experiments. We use this physical description to implement a computational thermostat [3]. References [1] SL Jacob, M Esposito, JMR Parrondo, F Barra, Thermalization induced by quantum scattering, PRX Quantum 2, 020312 (2021). [2] SL Jacob, M Esposito, JMR Parrondo, F Barra, Quantum scattering as a work source, Quantum 6, 750 (2022). [3] J Tabanera, I Luque, SL Jacob, M Esposito, F Barra, JMR Parrondo, Quantum collisional thermostats, New Journal of Physics 24, 023018 (2022).